KR102170891B1 - Method of production of thermoelectric micro-coolers(variants) - Google Patents

Abstract

The present invention relates to a thermoelectric device, and may be preferably used in the manufacture of a thermoelectric cooler applicable to wireless electronic devices, medicine, and devices used in repetitive temperature cycling (heat-cooling) conditions. A method of manufacturing a thermoelectric micro-cooler includes forming a first conductive layer including conductive traces on a first ceramic wafer; Soldering the thermoelectric material leg to the conductive trace of the first conductive layer; Forming a second conductive layer including conductive traces on the temporary wafer; Soldering the conductive trace of the second conductive layer to a leg of a thermoelectric material; Applying a protective coating on the thermoelectric material leg and the soldering joint; Etching the temporary wafer; Applying an elastically conductive adhesive layer on the second ceramic wafer; And adhering the second ceramic wafer to the conductive traces of the second conductive layer. The technical effect is to eliminate thermal shock to the elastic heat-conducting adhesive, thereby improving the thermal cycling resistance of the TEC and facilitating the formation and placement of a conductive layer on the leg of the thermoelectric material.

Description

Manufacturing method of thermoelectric microcooler (modified product) {METHOD OF PRODUCTION OF THERMOELECTRIC MICRO-COOLERS(VARIANTS)}

The present invention relates to a thermoelectric device, and may be preferably used in the manufacture of a thermoelectric cooler applicable to wireless electronic devices, medicine, and devices used in repetitive temperature cycling (heat-cooling) conditions.

Thermoelectric coolers (TECs) are known (2009) with thermoelectric material legs and ceramic heat wafers connected to the cooler via a switch bus for advantageous use in repetitive thermal cycling environments (2009). See Russian patent 81379 U1 (IPC H01L35/28) published March 10). Each switch bus is mounted on at least one ceramic wafer, which is bonded to it by means of thermal contact connections made of a single layer of an elastic adhesive compound or an additional adhesive sublayer. Known methods of making coolers include the following steps:

-Soldering the thermoelectric material leg to the switch bus of the lower ceramic wafer of the TEC,

-Applying an adhesive layer on the upper ceramic wafer using a screen printing method,

-Bonding the switch bus to the upper ceramic wafer,

-Soldering the upper ceramic wafer provided with the bonded switch bus to the lower ceramic wafer provided with thermoelectric material legs.

This manufacturing method has several important drawbacks. This method requires individual fabrication of the switch bus with each solder coating on the leg of thermoelectric material. Bonding the switch bus to the top ceramic wafer is a labor intensive process. While soldering the switch bus, the adhesive compound of the thermoelectric leg is subjected to a significant temperature shock (above 200 °C). In addition, known methods relate to so-called "large" TECs with fairly large geometric dimensions (the legs of such modules have a cross-sectional size of 1 × 1 mm 2 or more, and the ceramic members have dimensions of 15 × 15 mm 2 or more). Large legs and ceramics facilitate the assembly of these TECs. Because in this case the large dimensions provide a way to use conductive traces in the form of individual components ("buses") that are easily installed and glued to the rest of the TEC part.

The method chosen as the prototype is a known invention for producing a thermoelectric micro cooler (see U.S. Patent 6127619 (IPC H01L 35/28, H01L 35/34) published on Oct. 3, 2000),

-Manufacturing a conductive trace on the first ceramic wafer,

-Fabricating a leg of thermoelectric material on the conductive trace of the first ceramic wafer,

-Preparing a topology layer of conductive traces on the leg of thermoelectric material,

-Adhering a second ceramic wafer on top of the conductive traces.

The disadvantage of the method of manufacturing such a thermoelectric micro cooler is that it is not ready for the repeated temperature cycling process of the finished micro cooler. In addition, the use of individual switch buses in microcoolers is associated with a number of complex issues in terms of their compact dimensions and the production, positioning and bonding processes of these buses.

An object of the present invention is to solve the technical problem by providing a small thermoelectric cooler with improved reliability.

The technical effect achieved by the present invention provides the purpose of excluding thermal shock to the elastic heat-conducting adhesive, improving the thermal cycling resistance of the TEC, and facilitating the formation and placement of a conductive layer on the leg of the thermoelectric material. do.

This technical effect may include forming a first conductive layer including conductive traces on a first ceramic wafer; Soldering the thermoelectric material leg to the conductive trace of the first conductive layer; Forming a second conductive layer including conductive traces on the temporary wafer; Soldering the conductive trace of the second conductive layer to the leg of the thermoelectric material; Applying a protective coating on the thermoelectric material leg and the soldering joint; Etching the temporary wafer; Applying an elastically conductive adhesive layer on the second ceramic wafer; This is achieved by a method of manufacturing a thermoelectric micro-cooler comprising adhering a second ceramic wafer to a conductive trace of a second conductive layer.

Optionally, between etching the temporary wafer and applying the elastically conductive adhesive layer on the second ceramic wafer, an additional step of applying the adhesive layer on the second ceramic wafer and the conductive traces of the second conductive layer is provided.

Additionally, in parallel with the step of adhering the second ceramic wafer to the conductive traces of the second conductive layer, a step of controlling the thickness of the adhesion layer is further performed.

According to a second embodiment, a method of manufacturing a thermoelectric micro-cooler includes: forming a first conductive layer including conductive traces on a first ceramic wafer; Soldering the thermoelectric material leg to the conductive trace of the first conductive layer; Forming a second conductive layer including conductive traces on the temporary wafer; Soldering the conductive trace of the second conductive layer to the leg of the thermoelectric material; Mechanically removing the temporary wafer; Applying an elastically conductive adhesive layer on the second ceramic wafer; Adhering the second ceramic wafer to the conductive traces of the second conductive layer.

Hereinafter, the present invention will be described in detail with reference to the drawings showing steps of a method of manufacturing a thermoelectric micro cooler.
1 is a step of soldering a leg of a thermoelectric material to a conductive trace of a first conductive layer.
2 is a step of forming a second conductive layer including conductive traces on a temporary wafer.
3 is a step of soldering a conductive trace of a second conductive layer to a leg of a thermoelectric material.
4 is a step of etching a temporary wafer.
5 is a schematic diagram of the micro cooler after the etching step.
6 is a step of bonding a second ceramic wafer.
7 is a comparative plot of test results for a thermoelectric cooler.

The method is implemented as described below. A first conductive layer including a first conductive trace 2 is formed on a first ceramic wafer 1 which is a ceramic material substrate. The N-type thermoelectric material leg 3 and the P-type thermoelectric material leg 4 are soldered to the conductive trace 2 on the formed conductive layer by using a solder paste 5. Thereafter, the temporary wafer 6 having the second conductive layer formed thereon to include the second conductive trace 7 is soldered to the thermoelectric material legs 3 and 4. The temporary wafer 6 may be polyimide, lavsan, or any other material that temporarily supports the conductive traces 7 in the foregoing description, and which must be further mechanically or chemically removed. The second conductive layer comprising the second conductive traces 7 may be adhered to the temporary wafer 6, buried or burnt-into. Before chemically removing the temporary wafer 6 through group etching, the thermoelectric material legs 3 and 4 and the soldering joint 5 are protected by a protective coating (the coating is carried out by a group method). ) Protected from the etching solution. The temporary wafer 6 is etched. As another option to remove the temporary wafer 6, the second conductive traces 7 are soldered to the thermoelectric legs 3, 4 and then mechanically removed (eg tearing off). Thereafter, a lower layer of adhesive (not shown) is applied on both surfaces to be bonded together to the second ceramic wafer 9 and the conductive trace 7. This step is optional, but the presence of an adhesive sublayer helps to improve TEC reliability due to improved mechanical strength, which is about 50% higher than that obtained by making without the sublayer. In the next step, the elastic conductive adhesive layer 8 is applied to the second ceramic wafer 9, for example by a screen printing method or a continuous layer. In the final step, the second ceramic wafer 9 is adhered to the structure formed including the conductive traces 7 by means of an elastic conductive adhesive 8, and the thickness of the adhesive layer is controlled in the range of 30 μm to 50 μm. Due to the adhesive layer that makes the thermoelectric micro cooler elastic, it is possible to compensate for the thermodynamic stress of the module that occurs during the repetitive thermal cycling process.

In the final step of the above-described method, by adhering the second ceramic wafer 9, the adhesive 8 cannot be exposed to temperatures exceeding 50° C. during manufacture of the micro cooler. This is because the upper limit of the operating temperature of most adhesives is up to 200 °C, and when the temperature of these adhesives exceeds the limit of 200 °C, the physical and chemical properties (for example, elasticity) of the adhesive layer cannot be preserved. It is beneficial for the elasticity of the material.

detailed Example

Module 1MDL06-050-03 was produced according to both the standard technique (no adhesive layer) and the method of the present invention.

Table 1 shows a comparison of the properties of these modules.

number Measured
parameter system Measure
mode Measurement result TEC manufactured according to the invention of the present invention Standard TEC One R _AC , Ohm DX4190 Z-Meter In the air
T= 27℃ 0.85 0.91 2 Ζ×1000,
1/Κ 2.63 2.65 3 τ, sec 0.27 0.27 4 At 4.5A, ΔT, K Direct measurement
system
DX8020 Fixed current
In value
Expert
(expert) 60.74 57.56 5 ΔT, K work
At the point
Expert
(expert) 40 40 6 Q, W 0.3 0.3 7 Ι, Α 1.990 1.964 8 U, V 2.336 2.473 9 W, W 4.649 4.857

The table above shows the following contents:

-In TEC, the electric resistance R _AC is 7% different,

-Thermoelectric performance index Z is better than standard TEC (0.8% difference),

-The temperature drop △ T at a fixed current value of 4.5A is higher than that of the TEC manufactured according to the method of the present invention,

-The power consumption W at the operating point is lower (4.5% difference) for the TEC manufactured according to the method of the present invention.

As such, it can be said that a TEC manufactured according to the method of the present invention has the same electrical parameters as a similar standard TEC.

The module 1MC06-126-05 manufactured according to the method of the present invention as well as the standard module (adhesive layer member) can be subjected to a comparative test regarding resistance to the temperature cycling process. The parameters of the test are as follows:

-Base (high temperature side of TEC) temperature-40 ℃,

-Upper temperature of the low temperature side of TEC-100 ℃,

-The lower temperature of the low temperature side of TEC-20 ℃,

-Cycling speed-2 cycles per minute.

7 shows intermediate test results for modules manufactured according to the standard (gray) method and the method of the present invention (black). It can be seen that the electrical resistance of more than half of the standard module (adhesive bonding member) exceeds the 5%-limit, ie the standard module fails this test. At the same time, the electrical resistance of all TECs according to the method of the present invention is within the 5% criterion.

In the TEC according to the second embodiment of the present invention in which the wafer 6 is mechanically removed, the adhesive is only partially removed (the temporary wafer 6 and the conductive trace 7 of the conductive layer adhered thereto are separated by a mechanical method. Or the thermoelectric material legs 3 and 4 may be damaged (when the temporary wafer 6 and the conductive trace 7 of the buried/burnt-in conductive layer are separated by a mechanical method). Because there is, it has a lower characteristic. However, despite some drawbacks, the method of manufacturing such a micro cooler can be implemented on an industrial scale.

Claims (4)

In the method of manufacturing a thermoelectric micro-cooler,
-Forming a first conductive layer including conductive traces on the first ceramic wafer,
-Soldering the thermoelectric material leg to the conductive trace of the first conductive layer,
-Forming a second conductive layer including conductive traces on the temporary wafer,
-Soldering the conductive trace of the second conductive layer to the leg of the thermoelectric material,
-Applying a protective coating on the thermoelectric material leg and the soldering joint,
-Etching the temporary wafer,
-Applying an elastic heat-conductive adhesive layer on the second ceramic wafer,
-Adhering the second ceramic wafer to the conductive traces of the second conductive layer. The method of claim 1,
Between the step of etching the temporary wafer and the step of applying the elastic thermally-conductive adhesive layer on the second ceramic wafer, an additional step of applying an adhesive layer on the conductive trace of the second conductive layer and the second ceramic wafer is provided. How to be. The method of claim 1,
In parallel with the step of adhering the second ceramic wafer to the conductive trace of the second conductive layer, the step of controlling the thickness of the adhesion layer is performed. In the method of manufacturing a thermoelectric micro-cooler,
-Forming a first conductive layer including conductive traces on the first ceramic wafer,
-Soldering the thermoelectric material leg to the conductive trace of the first conductive layer,
-Forming a second conductive layer including conductive traces on the temporary wafer,
-Soldering the conductive trace of the second conductive layer to the leg of the thermoelectric material,
-Removing the temporary wafer by a mechanical method,
-Applying an elastic heat-conductive adhesive layer on the second ceramic wafer,
-Adhering the second ceramic wafer to the conductive traces of the second conductive layer.

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